AMD's Radeon RX 480 graphics card reviewed

We've been hearing about AMD's next-generation Polaris GPUs for a little over six months now. We knew those chips would have enhanced display output capabilites, and we also knew they would be produced using 14-nm FinFET process technology. Now, the first product to use this new architecture is here. The Polaris 10 GPU on AMD's Radeon RX 480 graphics card isn't a high-end monster like the GP104 chip powering Nvidia's first 16-nm FinFET cards, though. Instead, the RX 480 puts a $200-and-up price tag on VR-ready performance.

AMD sees a great deal of opportunity to regain market share in the $100-$300 graphics card price range, and the RX 480 is the company's first shot at the middle of the enthusiast bell curve. Let's see how it intends to join this battle.

Baby, you're a star
Polaris is actually a pair of chips—Polaris 10 and Polaris 11—that are two takes on the same underlying architecture. Both Polaris 10 and Polaris 11 will be making their way into desktops, but Polaris 11 is a smaller chip that will probably find a home in many more gaming laptops than it does desktop PCs.

ROP
pixels/
clock

Texels
filtered/
clock
(int/fp16)

Shader
processors

Rasterized
triangles/
clock

Memory
interface
width (bits)

Estimated
transistor
count
(Millions)

Die size
(mm²)

Fab
process

Polaris 11

16

64/32

1024

2

128

???

???

14 nm

Tonga

32

128/64

2048

4

256

5000

355

28 nm

Polaris 10

32

144/72

2304

4

256

5600

232

14 nm

Hawaii

64

176/88

2816

4

512

6200

438

28 nm

GM206

32

64/64

1024

2

128

2940

227

28 nm

GM204

64

128/128

2048

4

256

5200

398

28 nm

GP104

64

160/160

2560

4

256

7200

314

16 nm

As you can see from the table above, Polaris 10 occupies a much smaller footprint than Tonga before it. Despite its smaller area, Polaris 10 has a bit more of almost everything on board: more stream processors, more texturing units, two times the L2 cache of older chips at 2MB, and a variety of neat tricks that we'll discuss momentarily.

Source: AMD

The block diagram above should be largely familiar to anybody who's laid eyes on AMD's past GCN chips. Polaris 10 has 36 GCN compute units for a total of 2304 stream processors. It has 144 texturing units, four geometry engines, 32 ROPs, and a 256-bit path to GDDR5 memory. From a pure resource standpoint, this part falls somewhere between Tonga and Hawaii in the AMD pantheon.

Source: AMD

Polaris 11 is, at a glance, a little less than half of Polaris 10. It has half the ROPs, less than half of the shaders, half the triangles per clock, and a memory bus that's half as wide. It also has 1MB of L2 cache. It'll almost certainly be smaller than Polaris 10's 232-mm² die, and AMD further notes that this chip is its thinnest GPU ever. That may sound like a weird claim to make, but it's important for achieving the kind of console-class gaming experiences in thin-and-light notebooks that AMD wants to deliver with this architecture. Aside from one desktop card, we don't really know where Polaris 11 will land or what names it'll carry yet. The spotlight is on the Radeon RX 480 for today.

Now that we've seen the two basic Polaris parts, let's examine the common improvements that AMD baked into the underlying architecture.